The present invention is directed to an amplifier circuit which solves the problem of how highly capacitative loaded lines within integrated GaAs circuits (as occur, in particular, in memory modules) can be charge-reversed in an optimally short time. Limiting a predetermined high level to a defined value is also guaranteed.
Prior art solutions are inadequate with regards to this problem and have the disadvantages set forth below.
The circuit shown in FIG. 1, (see, Yokoyama N., Onodera Hl, Shinoki T., Ohnishi H., Nishi H., "A 3-ns GaAs 4 kx 1-bit static RAM", IEEE Trans. Electron, Devices, Vol. Ed-32 (1985) 9, pages 1797-1801) is merely an inverter T11, T21 of a standard type that must be dimensioned especially large because of the high load. This causes a high current consumption. When a limitation of the high level is required, an additional (relatively large) clamp diode D1 must be provided.
The circuits of FIG. 2, (Katano F., Takahashi K., Uetake K., Ueda K., Yamamoto R., Higashisaka A., "Fully decoded GaAs 1 kB static RAM using closely space electrode FETs", IEEE IEDM; 1983, pages 336-339; Toyoda N., Kanazawa K., Terada T., Mochizuki M., Ikawa Yasuo, Hojo A., "A 256.times.4 GaAs static RAM", IEEE GaAs Symposium, 1983, pages 86-89) and FIG. 3, (Mead C., Conway L., "Introduction to VLSI systems, Reading", Addison Wesley, pages 17-18, 1980) are an improvement with reference to power consumption, since a switch to a low level occurs during a low level at the output of the gate of T32 (FIG. 2) or T33 (FIG. 3). As a result the current through T32 or T33 is considerably reduced. However, since T32 and T33 are NON-transistors (normally on transistors) a forward current that cannot be ignored still flows through T32 and T42 or through T33 and T43. A relatively large clamp diode D2 or D3 must likewise be provided for limiting the high level, requiring space and acting like an additional capacitative load.
The circuit of FIG. 4 (see Takonos., Tanino N., Yoshihara T., Mitsui Y., Nishitani K. "A GaAs 1-kbit static RAM with a shallow recessed-gate structure FET", IEEE Trans. Electron Devices, Vol. Ed-32 (1985), 6, pages 1135-1139) is most favorable with respect to power consumption. However, it does not achieve the full high level at the output since the transistor T34 acts as a source follower whose source potential always lies below the gate potential by at least a threshold voltage. As a consequence of the gate-source diode of T24, the gate potential of T34 cannot exceed the high level.